But the asteroid, designated 2002 MN, is not in the same league as potential killer rocks measuring more than 0.6 miles (1 km) in diameter, some of which are known to lurk in our space neighborhood between Mars and Venus.

"2002 MN is a lightweight among asteroids and incapable of causing damage on a global scale, such as the object associated with the extinction of the dinosaurs," the NEO center said in a statement.

2002 MN was first spotted on June 17 by scientists with the Lincoln Near Earth Asteroid Research (LINEAR) project in Socorro, New Mexico, three days after it gave the Earth a close shave.

Nevertheless, the big boulder should not pose a risk for some time.

"This asteroid is not something to worry about," said Donald Yeomans, head of the Near Earth Objects program office at NASA's Jet Propulsion Laboratory in Pasadena, California. "We have calculated its orbit several decades into the future and it does not threaten Earth."

The closest near collision in recent decades took place in 1994, when asteroid 1994XL1 passed within 65,000 miles (105,000 km) of our planet.